A diagnostic apparatus for human body for use in each home, clinic, and the like requires a reduced price, a reduced size, a shortened test time, convenience of operation, and the like. Examples of a diagnostic apparatus which satisfies such requirements include a sensor device formed in a semiconductor integrated circuit (for example, NPL 1 and NPL 2).
FIG. 20 shows a conventional sensor device disclosed in NPL 1 and NPL 2. As shown in FIG. 20, a sensor device 10 is formed in a semiconductor integrated circuit and includes an oscillation unit 11 and an oscillation frequency detection unit 12. The oscillation unit 11 includes a resistor R1 and a resonator 13. The resonator 13 includes cross-coupled transistors M1 and M2, inductors L1 and L2, two sensing electrodes 14 to be brought into contact with an analyte 20, and a capacitor C3. The resonance frequency of the resonator 13 is 6 GHz to 30 GHz.
FIG. 21 shows a perspective view illustrating the two sensing electrodes 14. Moreover, FIG. 22 shows a sectional view illustrating plate-shaped electrodes 141 and 142 and peripheral members taken along line A-A in the arrow direction of FIG. 21. As illustrated in FIG. 21, each sensing electrode 14 includes the two plate-shaped electrodes 141 and 142 each having a rectangular parallelepiped shape.
As illustrated in FIG. 22, the plate-shaped electrodes 141 and 142 are formed in a metal wiring layer which is the uppermost layer of a semiconductor integrated circuit. Moreover, an interlayer insulating film 16 is disposed between metal wiring layers of the semiconductor integrated circuit. In FIG. 22, only the uppermost metal wiring layer and the interlayer insulating film 16 under the uppermost metal wiring layer are shown for the sake of convenience. The interlayer insulating film 16 has a surface covered with a surface protection film 15, and the surface protection film 15 has openings in regions where the two plate-shaped electrodes 141 and 142 are disposed. Thus, exposed upper surfaces of the late-shaped electrodes 141 and 142 directly come into contact with the analyte 20.
Next, operation of the sensor device 10 will be described. When the permittivity of the analyte 20 located in the vicinity of the sensing electrodes 14 changes, a parasitic capacitance value with respect to the sensing electrodes 14 changes, and the resonance frequency of the resonator 13 changes. A change of the oscillation frequency of the oscillation unit 11 alone with the change of the resonance frequency is detected by the oscillation frequency detection unit 12. The above-described operation enables the sensor device 10 to detect the change of the permittivity occurred in the analyte 20 located in the vicinity of the sensing electrodes 14 as the change of the oscillation frequency of the oscillation unit 11.